The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Directional solidification of multi-crystalline ingots is used to grow silicon material in either square or round shapes. The ingots are then shaped into ring-shaped blanks and further machined to make parts. For example, the parts may be used as components inside substrate processing systems for deposition, etching or other treatment of substrates such as semiconductor wafers.
There are several problems with the current technology. For example, most inefficiently use silicon material. A shape of the ingot that is grown is usually different than a shape of the part to be machined. As a result, significant machining of excess material is required. Other issues include removal of outer material on square ingots and removal of a central core from round or square ingots. The removed material is wasted.
Crucible coatings may be used to prevent sticking and to allow release of ingots from crucibles. However, the coatings are a source of contamination. A typical process involves the melting, stabilization, freezing, and annealing of ingots all in a sequence, in the same hotzone/crucible. The complexity reduces throughput. While current processes for ingot growth can be used to produce a solid ingot, they generally do not allow production of a near net shape ingot.